Magnetic Field Position Tracking System Drift Reduction
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Solution Overview
Problem
Existing motion tracking systems for user-interface devices face challenges with accuracy and cost due to reliance on mechanical assemblies, calibration complexities, and errors from consumer-grade sensors, particularly accelerometers and gyroscopes, leading to drift and inaccuracy in tracking user-induced motion over extended periods.
Innovation Solution
A motion tracking system utilizing a permanent magnet to generate a predictable magnetic field, combined with an electromechanical assembly including a gyroscope, accelerometer, magnetometer, and microprocessor, which uses dead-reckoning inertial measurement and magnetic field analysis to accurately determine position and orientation, allowing for accurate motion tracking with consumer-grade sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical assemblies with rolling elements are used to track motion, then motion tracking capability is achieved, but the system becomes costly, complex, and subject to wear and mechanical failure
Solution Approach 1:
The patent replaces the mechanical rolling element system with an optical measurement system using light sources, light sensors, and image processing to track motion, thereby eliminating mechanical wear and failure while maintaining motion tracking capability
Solution Approach 2:
The patent creates an optical copy or representation of surface features through light reflection and imaging, allowing motion to be tracked by comparing successive images rather than through direct mechanical contact
2Reliability
If optical measurements are used on transparent or smooth surfaces, then mechanical wear is eliminated, but consistent measurements become impossible due to insufficient surface features
Solution Approach 1:
The patent applies a calibration process before normal operation to establish the relationship between light source position and sensor readings, enabling the system to compensate for surface characteristics and achieve consistent measurements on transparent or smooth surfaces
Solution Approach 2:
The patent incorporates an adjustment mechanism that allows the light source position to be dynamically changed during calibration to optimize detection of surface features for specific surface types
3Ease of manufacture
If consumer-grade accelerometers and gyroscopes are used for motion tracking, then cost is reduced, but drift and inaccuracy occur over extended periods
Solution Approach 1:
The patent uses light sensor measurements of surface features as feedback to continuously correct and update position calculations, compensating for drift that accumulates in consumer-grade inertial sensors over time
Solution Approach 2:
The patent combines inertial measurement from accelerometers and gyroscopes with optical measurement from light sensors to create a hybrid system that leverages the advantages of both approaches while mitigating their individual weaknesses
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate and cost-effective motion measurement for user-input devices, such as smartphones, by combining inertial and magnetic measurements to reduce drift and enhance tracking precision, making it suitable for controlling cursors or game inputs.
Implementation Method 1
an external permanent magnet that generates a known or predictable magnetic field
Implementation Method 2
a magnetometer...measures this motion and sends relative displacement or other motion information
Data Source
AI summary
A common method for providing user-input to an electronic system consists of tracking the position and motion of an object moved by the user and conveying this information to the electronic system. One embodiment of a positional tracking system for an object has an external and stationary magnetic-field emitter, a magnetic-field sensor which moves with the tracked object, and a microprocessor that compares magnetic-field intensity measurements taken by the sensor and compares it to magnetic-field characteristics defined for the external magnetic field emitter. A nonlinear equation solver, particle filter, or other method is used to determine the position of the sensor in the magnetic field. In this way the position of an object can be tracked using a single magnetic field emission source. This positional information can be combined with an inertial tracking system to mitigate drift errors.